Papers by Jean-pierre Hulin
Oxford University Press eBooks, Jan 20, 2015
Dieses Kapitel ist dem Studium der Bewegungsformen eines Fluids gewidmet, insbesondere seinen Def... more Dieses Kapitel ist dem Studium der Bewegungsformen eines Fluids gewidmet, insbesondere seinen Deformationen, ohne jedoch auf die Ursachen einzugehen, die im anschliesenden Kapitel untersucht werden. Wir beginnen mit einigen Grundlagen zur Beschreibung der Fluidbewegungen (§3.1) (Definition der Geschwindigkeit eines Fluidteilchens, Eulersche und Lagrangesche Beschreibung, Beschleunigung, charakteristische Linien in einer Stromung). Danach untersuchen wir die Deformationen eines Fluids (§ 3.2). Dabei werden sich viele Analogien zu den Deformationsproblemen in der Festkorpermechanik finden. Im folgenden Abschnitt (§ 3.3) begrunden wir die Massenerhaltungsgleichung und die Inkom-pressibilitatsannahmefur ein Fluid (diese Bedingung wird das ganze Buch hindurch erfullt sein). Wir werden in diesem Zusammenhang ebenfalls verschiedene Analogien zum Elektromagnetismus andeuten, die in den folgenden Kapiteln prazisiert werden. In Abschnitt(§ 3.4) fuhren wir die Stromfunktion fur planare und axialsymmetrische Stromungen ein und betrachten einige Beispiele planarer Stromungen sowie die zugehorigen Formen der Stromlinien. Wir beschliesen (§ 3.5) dieses Kapitel mit der Beschreibung verschiedener experimenteller Methoden zur Messung von Geschwindigkeit und Geschwindigkeitsgradienten einer Fluidstromung.
EDP Sciences eBooks, 2001
Applied Mechanics Reviews, Sep 1, 2002
Physics of Fluids, Apr 1, 2019
We study numerically the three-dimensional (3D) dynamics of two facing flows in an X-shaped junct... more We study numerically the three-dimensional (3D) dynamics of two facing flows in an X-shaped junction of two circular channels crossing at an angle α. The distribution of the fluids in the junction and in the outlet channels is determined as a function of α and the Reynolds number Re. Our goal is to describe the different flow regimes in the junction and their dependence on α and Re. We also explore to which extent two-dimensional (2D) simulations are able to describe the flow within a 3D geometry. In the 3D case, at large Re's (≳50) and α's (≳60 ○), axial vorticity (i.e., parallel to the outlet axis) of magnitude increasing both with α and Re develops in the outlet channels and cannot be reproduced by 2D numerical simulations. At lower angles (α ≲ 60 ○), instead, a mean vorticity component perpendicular to the junction plane is present: both its magnitude and the number of the corresponding vortices (i.e., recirculation zones) increase as α decreases. These vortices appear in both 2D and 3D simulations but at different threshold values of α and Re. At very low Re's (≲5) and α's (∼15 ○), the flow structure in 3D simulations is nearly 2D but its quantitative characteristics differ from 2D simulations. As Re increases, this two-dimensionality disappears, while vortices due to flow separation appear in the outlet channels.
Physical review, May 23, 2001
Miscible fluid displacements are studied experimentally in a radial flow between two complementar... more Miscible fluid displacements are studied experimentally in a radial flow between two complementary replica of a self-affine rough granite fracture surface. The displacement front between a dyed fluid and a transparent ͑but otherwise identical͒ one is followed optically through one face of the cell. The evolution of its geometry is studied as a function of time, flow-rate, and normal and lateral relative displacements between the two surfaces. For a purely normal displacement, the front is globally smooth, due to the constant local distance between surfaces. For a finite lateral displacement, the front is rough due to spatial variations of this distance; its geometry is fractal and its dimension is directly related to the Hurst exponent HϷ0.8 of the surface. The fractal regime is observed only above a lower cutoff scale that depends on the normal spacing of the surfaces and an upper one that increases with the injected volume and with the amplitude of the lateral displacement.
Journal of Contaminant Hydrology, Dec 1, 2000
An experimental study of the transport properties of fluid-saturated joints composed of two compl... more An experimental study of the transport properties of fluid-saturated joints composed of two complementary rough fracture surfaces, translated with respect to each other and brought in contact, is reported. Quantitative roughness measurements on different fractured granite samples show that the surfaces have a self-affine geometry from which the dependence of the mean aperture on the relative displacement of fracture surfaces kept in contact can be predicted. Variations of the hydraulic and electrical conductances of the joint are measured as functions of its mean aperture. A simple parallel plane model accounts for the global trend of the measurements, but significant deviations are observed when a relative lateral displacement of the surfaces is introduced. A theoretical analysis of their origin shows that they are due both to the randomness of the aperture field and to a nonzero local slope of the surface near the injection hole; the corresponding conductivity fluctuation amplitudes have power law and linear variations with the lateral displacement, and are enhanced by the radial injection geometry.
Oxford University Press eBooks, Jan 20, 2015
HAL (Le Centre pour la Communication Scientifique Directe), Mar 31, 2008
The influence of a small relative density difference (≃ 3.10 −4) on the displacement of two misci... more The influence of a small relative density difference (≃ 3.10 −4) on the displacement of two miscible liquids is studied experimentally in transparent 2D networks of micro channels with a mean width a held vertically. Maps of the local relative concentration are obtained by an optical light absorption technique. Both stable displacements in which the denser fluid enters at the bottom of the cell and displaces the lighter one and unstable displacements in which the lighter fluid is injected at the bottom and displaces the denser one are realized. Except at the lowest mean flow velocity U, the average C(x, t) of the relative concentration satisfies a convection-dispersion equation. The relative magnitude of |U | and of the velocity Ug of buoyancy driven fluid motions is characterized by the gravity number Ng = Ug/|U |. At low gravity numbers |Ng| < 0.01 (or equivalently high Péclet numbers P e = U a/Dm > 500), the dispersivities l d in the stable and unstable configurations are similar with l d ∝ P e 0.5. At low velocities (|Ng| > 0.01), l d increases like 1/P e in the unstable configuration (Ng < 0) while it becomes constant and close to the length of individual channels in the stable case (Ng > 0). Iso concentration lines c(x, y, t) = 0.5 are globally flat in the stable configuration while, in the unstable case, they display spikes and troughs with an rms amplitude σ f parallel to the flow. For Ng > −0.2 σ f increases initially with the distance and reaches a constant limit while it keeps increasing for Ng < −0.2. A model taking into account buoyancy forces driving the instability and the transverse exchange of tracer between rising fingers and the surrounding fluid is suggested and its applicability to previous results obtained in 3D media is discussed.
Bulletin of the American Physical Society, Nov 23, 2015
GMP (FI-UBA)-We found that a cylinder confined between two parallel plates displays a fluttering ... more GMP (FI-UBA)-We found that a cylinder confined between two parallel plates displays a fluttering instabilities. The cylinder oscillates with respect to the horizontal. The characteristics of the instability (frequency, amplitude...) are found to be function of the Froude number. Compared to previous studies, this instability is triggered by the confinement and not by inertial effects.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 2, 2001
APS, Nov 1, 2003
Variations of the apparent mass (M_app) at the bottom of a granular packing inside a vertical tub... more Variations of the apparent mass (M_app) at the bottom of a granular packing inside a vertical tube in relative motion are studied experimentally for a broad range of relative velocities (from 10 mu m/s to 100 mm/s). Apparent mass measurements with a relative motion are more reproducible than for static packings and the variation of M_app with the total mass
HAL (Le Centre pour la Communication Scientifique Directe), Oct 1, 2001
Objectifs : analyser la dynamique du mélange entre deux fluides miscibles de densités différentes... more Objectifs : analyser la dynamique du mélange entre deux fluides miscibles de densités différentes (et de même viscosité) superposés en configuration instable dans un long tube vertical : • digitation de type Rayleigh-Taylor • croissance de la hauteur de la zone de mélange en fonction du temps • nature diffusive ou convective du mélange Applications : • complétion des puits pétroliers (contrôler la contamination du ciment par la boue pour éviter de compromettre l 'étanchéité du puits) • colonnes d'extraction ou autres types de réacteurs continus Travaux antérieurs : • en cellule de Hele-Shaw, la largeur de la zone de mélange croît comme le carré du temps puis proportionnellement au temps • en tube vertical : études en configuration dissymétrique, sans la dépendance en temps des profils de concentration
Physics Bulletin, Jul 1, 1987
Oil engineers, a decade ago, would not have imagined a connection between the physicochemical pro... more Oil engineers, a decade ago, would not have imagined a connection between the physicochemical processes involved in oil recovery and statistical physics theories of percolation, random fields or fractal geometries. However, recent theoretical models such as invasion percolation have predicted that when oil and water move simultaneously in porous reservoir rocks the separation front may have a fractal geometry.
Journal of physics, May 1, 2009
The transport of flexible fibers by a flowing fluid has been studied experimentally in transparen... more The transport of flexible fibers by a flowing fluid has been studied experimentally in transparent model fractures. Both finite length segments (20mm &amp;amp;amp;amp;amp;amp;amp;lt;= l &amp;amp;amp;amp;amp;amp;amp;lt;= 150 mm) and continuous fibers penetrating freely into the model were used; their motion is monitored by means of a digital camera and of an image thresholding technique and is induced by the flow of
The addition of solid particles to a fluid can change significantly the way it flows. This is imp... more The addition of solid particles to a fluid can change significantly the way it flows. This is important in several practical situations like landslides produced by heavy rain, waste treatment and blood flow. In some cases, the presence of solid particles has been shown to accelerate mixing in viscous flows through small channels. In this work, we show that oscillatory flow induces an instability characterized by particle motion transverse to the main flow, which could help improve mixing. We perform experiments with non-Brownian spherical particles (diameter 40 µm) suspended in a viscous fluid subject to squarewave oscillations inside a channel of rectangular cross-section (gap 1 mm, width 10 mm). Using fluorescence we visualize and track the particles in a plane across the gap and along the length. After a number of oscillations, we observe small but significant displacements of the particles across the gap. These displacement have oscillatory and long-term drift components, both spatially periodic along the flow direction. The latter may account for the transverse deformation of a high particle volume fraction region present in the center of the channel. Finally, we define and characterize an onset time for this instability as a function of the oscillation amplitude and the volume fraction.
Physical Review Fluids
The behavior of neutrally buoyant, non-Brownian suspensions subject to square-wave flow oscillati... more The behavior of neutrally buoyant, non-Brownian suspensions subject to square-wave flow oscillations in Hele-Shaw cells is investigated. The velocity field across the cell gap is determined by tracking particles in a plane parallel to the main flow. Initially, the velocity field of the particles is parallel to the main flow and its profile across the gap is blunted due to a higher volume fraction of particles in the gap center; this has been confirmed by direct estimations of the particle fraction and likely results from shear-induced migration. Velocity fluctuations, both along and transverse to the flow direction, agree reasonably well with previous studies. At longer times, the suspension develops an instability characterized by the growth of a transverse velocity component that is periodic along the main flow direction and in time. No influence of inertia on the characteristic onset time of this instability is observed for Reynolds numbers varying over four decades below Re = 0.4. The inverse of the onset time increases linearly with the amplitude of the oscillatory flow. The dependence of the onset time on the particle volume fraction and the gap thickness is consistent with the characteristic time for particle migration across the gap due to shear-induced diffusion.
Bulletin of the American Physical Society, 2020
The motion of individual particles has been tracked experimentally in a non-Brownian suspension o... more The motion of individual particles has been tracked experimentally in a non-Brownian suspension of non-buoyant spheres (volume fraction between 0.2 and 0.4) subject to a squarewave oscillatory flow in a Hele-Shaw cell at low Reynolds numbers. We investigated the evolution of the suspension structure and velocity profile, as well as the microscopic reversibility of the particle trajectories, as a function of the amplitude A and period T of the oscillating flow. At short times, the flow is parallel with a blunted parallel velocity and a corresponding increase of particle concentration at the center of the channel, consistent with previous results and shear-induced migration models. The reversibility of the motion of the particles from one period to the next is strong in the center region but much weaker close to the walls. At longer times, an instability induces an exponential growth in the motion of the particles transverse to the flow, forming a periodic structure or recirculating zones along the channel. The wavelength and transverse velocity have been studied as a function of A and T. The reversibility of the particle motion is strongly reduced in this regime. We also discuss the presence of a threshold value in the cumulative strain for the appearance of the instability.
Uploads
Papers by Jean-pierre Hulin